Herein,
we present the synthesis and coordination chemistry of
copper(II) and zinc(II) complexes of two novel heterocyclic triazacyclononane
(tacn)-based chelators (HNODThia and NODThia-AcNHEt). The chelator HNODThia was further derivatized to
obtain a novel PSMA-based bioconjugate (NODThia-PSMA)
and a bifunctional photoactivatable azamacrocyclic analogue, NODThia-PEG
3
-ArN
3
, for the development of copper-64 radiopharmaceuticals. 64Cu radiolabeling experiments were performed on the different
metal-binding chelates, whereby quantitative radiochemical conversion
(RCC) was obtained in less than 10 min at room temperature. The in vitro stability of NODThia-PSMA in human
plasma was assessed by ligand-challenge and copper-exchange experiments.
Next, we investigated the viability of the photoactivatable analog
(NODThia-PEG
3
-ArN
3
) for the light-induced photoradiosynthesis
of radiolabeled proteins. One-pot photoconjugation reactions to human
serum albumin (HSA) as a model protein and the clinically relevant
monoclonal antibody formulation MetMAb were performed. [64Cu]Cu-7-azepin-HSA and [64Cu]Cu-7-azepin-onartuzumab were prepared in less than 15 min by irradiation
at 395 nm, with radiochemical purities (RCP) of >95% and radiochemical
yields (RCYs) of 42.7 ± 5.3 and 49.6%, respectively. Together,
the results obtained here open the way for the development of highly
stable 64Cu-radiopharmaceuticals by using aza-heterocyclic tacn-based chelators, and the method can easily be
extended to the development of 67Cu radiopharmaceuticals
for future applications in molecularly targeted radio(immuno)therapy.